It is well established that certain forms of hydrocarbons require upgrading in order to either transport them or enhance value for sale. Further, refineries are not suited to processing heavy oil, bitumen etc. and thus the viscosity, density and impurity content, such as heavy metals, sulfur and nitrogen, present in such heavy materials must be altered to permit refining. Upgrading is primarily focussed upon reducing viscosity, sulphur, metals, and asphaltene content in the bitumen.
One of the problems with heavy oil and bitumen upgrading is that the asphaltenes and the heavy fraction must be removed or modified to create value and product yield. Typical upgraders exacerbate the problem by the formation of petcoke or residuum which results in undesirable waste material. This material, since it cannot be easily converted by conventional methods, is commonly removed from the process, reducing the overall yield of valuable hydrocarbon material from the upgrading process.
The Fischer-Tropsch process has found significant utility in hydrocarbon synthesis procedures and fuel synthesis. The process has been used for decades to assist in the formulation of hydrocarbons from several materials such as coal, residuum, petcoke, and biomass. In the last several years, the conversion of alternate energy resources has become of great interest, given the escalating environmental concerns regarding pollution, the decline of world conventional hydrocarbon resources, and the increasing concern over tailings pond management, together with the increasing costs to extract, upgrade and refine the heavy hydrocarbon resources. The major producers in the area of synthetic fuels have expanded the art significantly in this technological area with a number of patented advances and pending applications in the form of publications. Applicant's co-pending U.S. application Ser. No. 13/024,925, teaches a fuel synthesis protocol and the entire contents of that application are incorporated herein for reference.
Examples of recent advances that have been made in this area of technology includes the features taught in U.S. Pat. No. 6,958,363, issued to Espinoza, et al., Oct. 25, 2005, Bayle et al., in U.S. Pat. No. 7,214,720, issued May 8, 2007, U.S. Pat. No. 6,696,501, issued Feb. 24, 2004, to Schanke et al.
In respect of other progress that has been made in this field of technology, the art is replete with significant advances in, not only gasification of solid carbon feeds, but also methodology for the preparation of syngas, management of hydrogen and carbon monoxide in a GTL plant, the Fischer-Tropsch reactors management of hydrogen, and the conversion of biomass feedstock into hydrocarbon liquid transportation fuels, inter alia. The following is a representative list of other such references. This includes: U.S. Pat. Nos. 7,776,114; 6,765,025; 6,512,018; 6,147,126; 6,133,328; 7,855,235; 7,846,979; 6,147,126; 7,004,985; 6,048,449; 7,208,530; 6,730,285; 6,872,753, as well as United States Patent Application Publication Nos. US2010/0113624; US2004/0181313; US2010/0036181; US2010/0216898; US2008/0021122; US 2008/0115415; and US 2010/0000153.
The Fischer-Tropsch (FT) process has several significant benefits when applied to a bitumen upgrader process, one benefit being that it is able to convert previously generated petcoke and residuum to valuable, high quality synthetic crude oil (SCO) with notably increased paraffinic content. A further significant benefit is that the raw bitumen yield to SCO is near or greater than 100%, a 20% yield increase relative to certain current upgrader processes. Another benefit is that there is no petcoke and residuum waste product to impact the environment thus improving overall bitumen resource utilization.
A further benefit of the application of the FT process to a bitumen upgrader is that a sweet, highly paraffinic and high cetane content synthetic crude oil (SCO) is produced. More specifically, beneficial byproducts of the FT process such as paraffinic naphtha and FT vapours (such as methane and liquid petroleum gases (LPG)), have particular value within the bitumen upgrader process and upstream unit operations. FT vapours, virtually free from sulphur compounds can be used as upgrader fuel or as feedstock for hydrogen generation to offset the requirement for natural gas. FT naphtha, primarily paraffinic in nature, can also be used in the generation of hydrogen, but further, due to its unique paraffinic nature, it can also be used as an efficient deasphalting solvent not readily available from current upgrader operations.
It has also been well documented that the use of FT paraffinic naphtha as a solvent for an oilsands froth unit improves the operation and efficacy of fine tailings and water removal at a reduced diluent-to-bitumen (D/B) ratio and relatively low vapour pressure. This has significant advantages in terms of lowering the size and cost of expensive separators and settlers and increasing their separation performance and capacity rating. This results in virtually dry bitumen froth feed (<0.5 basic sediment and water) to the upgrader, while improving impact on the tailings pond.
Having thus generally discussed the appropriateness of the Fischer-Tropsch technique in synthesizing syngas to FT liquids, a discussion of the prior art and particularly the art related to the upgrading and gasifying of heavy hydrocarbon feeds would be useful.
One of the examples in this area of the prior art is the teachings of U.S. Pat. No. 7,407,571 issued Aug. 5, 2008, to Rettger et. al. This reference names Ormat Industries Ltd. as the Assignee and teaches a process for producing sweet synthetic crude oil from a heavy hydrocarbon feed. In the method, the patentees indicate that heavy hydrocarbon is upgraded to produce a distillate feed which includes sour products and high carbon byproducts. The high carbon content byproducts are gasified in a gasifier to produce a syngas and sour byproducts. The process further hydroprocesses the sour products along with hydrogen gas to produce gas and a sweet crude. Hydrogen is recovered in a recovery unit from the synthetic fuel gas. The process also indicates that further hydrogen gas is processed and hydrogen depleted synthetic fuel gas is also produced. Further hydrogen gas is supplied to the hydroprocessing unit and a gasifying step is conducted in the presence of air or oxygen. The gas mixture is scrubbed to produce a sour water and a clean sour gas mixture. The sour gas mixture is subsequently processed to produce a sweet synthetic fuel gas and a hydrogen enriched gas mixture from the synthetic fuel gas using a membrane. The overall process is quite effective, however, it does not take advantage of the conversion of synthesized streams which are useful for introduction into the hydroprocessing unit for production of synthetic crude, the recycling of unique streams for use in the upgrader, nor is there any teaching specifically of the integration of the Fischer-Tropsch process or the recognition of the benefit to the process of using a SMR and/or ATR in the process circuit to maximize SCO yields and reducing dependence on natural gas.
Iqbal et. al. in U.S. Pat. No. 7,381,320 issued Jun. 3, 2008, teaches a process for heavy oil and bitumen upgrading. In overview, the process is capable of upgrading crude oil from a subterranean reservoir. The process involves converting asphaltenes to steam power, fuel gas, or a combination of these for use in producing heavy oil or bitumen from a reservoir. A portion of the heavy oil or bitumen are solvent deasphalted to form an asphaltene fraction and a deasphalted oil, referred to in the art as DAO as a fraction free of asphaltenes and with reduced metals content. The asphaltene fraction from the solvent deasphalting is supplied to the asphaltenes conversion unit and a feed comprising the DAO fraction supplied to a reaction zone of a fluid catalytic cracking (FCC) unit with an FCC catalyst to capture a portion of the metals from the DAO fraction. A hydrocarbon effluent is recovered from this having a reduced metal content. Similar to the process taught in U.S. Pat. No. 7,407,571, this process has utility, however, it limits the conversion of the otherwise wasteful asphaltene to production of solid fuel or pellets or conversion to syngas for fuel, hydrogen or electric power production. There is no teaching specifically integrating the Fischer-Tropsch process.
In U.S. Pat. No. 7,708,877 issued May 4, 2010 to Farshid et. al. there is taught an integrated heavy oil upgrader process and in line hydro finishing process. In the process, a hydroconversion slurry reactor system is taught that permits a catalyst, unconverted oil and converted oil to circulate in a continuous mixture throughout a reactor with no confinement of the mixture. The mixture is partially separated between the reactors to remove only the converted oil while allowing unconverted oil in the slurry catalyst to continue on to the next sequential reactor where a portion of the unconverted oil is converted to a lower boiling point. Additional hydro processing occurs in additional reactors for full conversion of the oil. The so called fully converted oil is subsequently hydrofinished for nearly complete removal of heteroatoms such as sulfur and nitrogen.
This document is primarily concerned with hydroconversion of heavy hydrocarbon, while not being suitable for bitumen upgrading. It also fails to provide any teaching regarding the use of Fischer-Tropsch process, usefulness of recycle streams, hydrogen generation or other valuable and efficient unit operations critical to successful upgrading of raw bitumen.
Calderon et. al. in U.S. Pat. No. 7,413,647 issued Aug. 19, 2008, teach a method and apparatus for upgrading bituminous material. The method involves a series of four distinct components, namely a fractionator, a heavy gas oil catalytic treater, a catalyst regenerator/gasifier and a gas clean up assembly. The patent indicates that in practicing the method, the bitumen in liquid form is fed to the fractionator for primary separation of fractions with the bulk of the bitumen leaving the bottom of the fractionator in the form of a heavy gas oil which is subsequently pumped to the catalytic treater and sprayed on a hot catalyst to crack the heavy gas oil, thus releasing hydrocarbons in the form of hydrogen rich volatile matter while depositing carbon on the catalyst. The volatile matter from the treater is passed to the fractionator where condensable fractions are separated from noncondensable hydrogen rich gas. The carbon containing catalyst from the treater is recycled to the regenerator/gasifier and the catalyst, after being regenerated is fed hot to the treater.
The method does not incorporate the particularly valuable Fischer-Tropsch process or provide a unit for effecting the Fischer-Tropsch reaction and further, the method is limited by the use of the catalyst which would appear to be quite susceptible to sulfur damage and from this sense there is no real provision for handling the sulfur in the bitumen.
In United States Patent Application, Publication No. US 2009/0200209, published Aug. 13, 2009, Sury et. al. teach upgrading bitumen in a paraffinic froth treatment process. The method involves adding a solvent to a bitumen froth emulsion to induce a settling rate of at least a portion of the asphaltenes and mineral solids present in the emulsion and results in the generation of the solvent bitumen-froth mixture. Water droplets are added to the solvent bitumen-froth mixture to increase the rate of settling of the asphaltenes and mineral solids. The focus of the publication is primarily to deal with the froth. There is no significant advance in the upgrading of the bitumen.
A wealth of advantages are derivable from the technology that has been developed and which is described herein. These are realized in a number of ways including:                i) near 100% or greater synthetic crude yield from heavy oil or bitumen without the wasteful production of petcoke or residuum;        ii) the synthetic crude oil (SCO) slate is higher quality, sweet light crude with more paraffinic and less aromatic and heavy gas oil components in the product slate;        iii) less natural gas is required to generate hydrogen for upgrading as the FT naphtha, FT vapours and hydroprocessing vapours can be recycled to generate a hydrogen rich syngas;        iv) pure hydrogen can be generated from the hydrogen rich syngas using membranes, absorption or pressure swing adsorption units, for use in the hydroprocessing (hydrocracking, isomerisation, hydrotreating) units;        v) Fischer-Tropsch (FT) liquids are primarily pariffinic in nature improving the quality and value of SCO product slate;        vi) FT naphtha is rarely available in any quantity in current upgraders and would be very preferentially used for deasphalting vacuum bottoms in a Solvent Deasphalting Unit (SDA) and in a Oilsands Froth Treatment Unit; and        vii) Concentrated CO2 is available from the gasifier (XTL) syngas treatment unit, allowing the upgrader to be a low cost carbon capture ready CO2 source for carbon capture and sequestration (CCS) projects.        